Clergy and staff of the Archdiocese of Cologne tried to browse pornography on work PCs, its archbishop has confirmed.
German media said around 1,000 attempts to view restricted sites were logged when the organisation ran a month of tests on its IT security systems.
At least one senior clergy member was among 15 people identified, the Kölner Stadt-Anzeiger newspaper reported.
The archbishop, Rainer Maria Woelki, said he had ordered an investigation that would deal with those responsible.
Watching pornography on archdiocese computers is strictly prohibited, as is accessing material on drugs and violence.
The majority of the suspicious activity concerned pornographic sites, according to the Kölner Stadt-Anzeiger.
In a statement supplied to the BBC by the archdiocese, Cardinal Woelki said he was "disappointed... that employees attempted to access pornographic sites".
An investigation had been launched so those responsible would be dealt with, as it was "important to me that not everyone be placed under general suspicion now", he added.
The archdiocese said the information referred to in the German press report was collated during a check of its IT security's ability to block access to sites that "pose a risk (violence, pornography, drugs, etc)".
It added there was "no evaluation of the specific content behind the URLs" in question, but there were "no indications of criminally relevant conduct".
The tests, conducted between May and June of last year, were not specifically aimed at investigating the behaviour of staff or clergy, it said.
Guido Assmann, the vicar-general of Cologne, said his organisation was "very aware" of the problem, but that he was "pleased that our security systems were effective".
Meanwhile, a website for the Catholic Church in Germany, Katholisch.de, reported that public prosecutors were investigating a layman identified among the 15 separately on suspicion of possessing "criminal content".
The archdiocese told the BBC it was co-operating "fully with the state authorities", and that the person concerned was "no longer active" in the organisation.
The reports come after a series of scandals that have engulfed the archdiocese, the largest in Germany with more than two million members.
A report in 2021 found there had been more than 200 abusers and more than 300 victims - mostly under the age of 14 - between 1975 and 2018 in the Cologne archdiocese area.
In June, police raided archdiocese property in an investigation into the Cardinal Woelki, who is accused of perjuring himself in an investigation into abuse committed by Winfried Pilz, a priest who ran a children's charity. Pilz died in 2019.
The archdiocese said the accusations against Cardinal Woelki needed to be proven or refuted.
Woelki last year offered his resignation to the Pope. Rome has not yet made a decision on whether to accept it.